According to ‘transformative’ theories of rationality, human rational mental capacities cannot be completely explained using the theories and concepts of natural science because rational mental states stand to one another in irreducibly normative relations of justification. Certain transformative theorists propose that a capacity counts as rational if a ‘Why?’ question is applicable to some exercises of that capacity. But ‘Why?’ questions are in principle applicable to any intentional action, like walking over there, or deliberately holding one’s breath. Transformative rationality therefore seems to entail that capacities for walking or breathing are rational and hence escape complete scientific explanation. Yet it would be surprising to learn that physiology, medicine, and biology could not completely explain such capacities. Given the ‘Why?’ question criterion for a rational capacity, there is a danger of ‘rationality’ creeping into capacities that (one might think) should submit to scientific explanation, and even into sub-individual processes. This is the ‘Problem of ‘Creeping Rationalism’’. After introducing the problem, I consider potential ways a transformative theorist could try to avoid the problem by limiting the scope of what capacities are ‘transformed’ by rationality. I argue that initially promising proposals to do this are either circular, or are incompatible with core commitments of the theory.